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1 Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Kangnam-Ku, Seoul 135-710, South Korea.
Received February 10, 2003;
accepted after revision March 19, 2003.
Address correspondence to J. H. Lim
(jhlim{at}smc.samsung.co.kr).
Introduction
 Top Introduction Pathologic and Imaging FindingsIntrahepatic CholangiocarcinomaExtrahepatic CholangiocarcinomaMode of SpreadClinical SignificanceReferences |
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Various terminology and classifications have been used to describe the pathologic and radiologic appearance of cholangiocarcinoma, and each describes a specific aspect of the tumor. However, some of the terminology and classifications are ambiguous and therefore confusing. Eggel [4] classified cholangiocarcinomas as nodular, massive, and diffuse, like hepatocellular carcinoma. Rosai [5] classified cholangiocarcinoma as polypoid and sclerosing. Weinbren and Mutum [6] classified cholangiocarcinoma into three types: nodular, sclerosing, and papillary. In the radiologic literature, hilar and extrahepatic cholangiocarcinomas have been classified as exophytic, infiltrating, and polypoid (or papillary) [7-9].
The Liver Cancer Study Group of Japan has proposed a new classification based on growth characteristics, with tumors being identified as mass-forming, periductal-infiltrating, and intraductal-growing types [10] (Figs. 1A, 1B, and 1C). This classification is considered to be the most reasonable because it describes the gross appearance, growing characteristics, biologic behavior, and prognostic implication for patients [11, 12] and because it is helpful for radiologic interpretation. According to this new classification, which I use for this review article, the exophytic or nodular type matches the mass-forming type, the infiltrating or sclerosing type matches the periductal-infiltrating, and the polypoid or papillary type matches the intraductal-growing type. The prognosis for mass-forming and periductal-infiltrating cholangiocarcinomas is generally unfavorable, whereas the prognosis for intraductal-growing cholangiocarcinoma is much better (or excellent) after surgical resection [11-14]. Precise characterization of these tumors in terms of their growth pattern and staging is mandatory for optimal treatment planning and for determining a prognosis. Surgical resection should be tailored depending on the morphologic type and the stage of the tumors [10]. In this regard, the morphologic classification of cholangiocarcinoma is important.
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Mass-forming intrahepatic cholangiocarcinoma and infiltrating extrahepatic cholangiocarcinoma and their imaging findings are well described in the literature [7, 8, 15]; intraductal-growing cholangiocarcinoma, however, is not. In this review, I describe the gross appearance of intrahepatic and extrahepatic cholangiocarcinomas, correlate the pathologic and imaging findings, consider the mode of spread of these tumors, and discuss the clinical significance of the various growth patterns of cholangiocarcinoma.
Pathologic and Imaging Findings
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TopIntroductionPathologic and Imaging FindingsIntrahepatic CholangiocarcinomaExtrahepatic CholangiocarcinomaMode of SpreadClinical SignificanceReferences |
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In a study by Sasaki et al. [11], more than half of the mass-forming intrahepatic cholangiocarcinomas were poorly differentiated, whereas most periductal-infiltrating cholangiocarcinomas were well differentiated. Most intraductal-growing cholangiocarcinomas have been classified as papillary adenocarcinomas [17-20].
Intrahepatic Cholangiocarcinoma
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TopIntroductionPathologic and Imaging FindingsIntrahepatic CholangiocarcinomaExtrahepatic CholangiocarcinomaMode of SpreadClinical SignificanceReferences |
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The most common appearance of peripheral intrahepatic cholangiocarcinoma on sonography, CT, and MRI is a well-defined, single, predominantly homogeneous mass with irregular borders [6, 15, 22, 23] (Fig. 3). Satellite or daughter nodules are frequent and vary in size [23] (Fig. 4). On contrast-enhanced CT or MRI, thin or thick, rimlike enhancement is frequently seen around the periphery of the tumor on arterial phase images and as gradual centripetal enhancement on delayed phase images [23-25] (Fig. 3). The entire mass may be enhanced only on delayed phase images, some hours after contrast administration. Some cholangiocarcinomas are depicted only on delayed phase images, and the tumors may be missed without them. These findings reflect the nature of the tumor, which is mainly desmoplastic. Capsular retraction is relatively frequent [23] (Fig. 3). The bile ducts peripheral to the tumor are usually dilated because of obstruction by the tumor. At other times, they may not be dilated, even if the tumor arises from one of the intrahepatic ducts [23].
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Imaging findings of mass-forming hilar cholangiocarcinomas appear basically the same as those of peripheral cholangiocarcinomas, except that they include intrahepatic bile duct dilatation [9, 26]. Most hilar cholangiocarcinomas result in obstruction of the right and left hepatic ducts, and a mass may override and separate the bile ducts [9, 26, 27].
Periductal-Infiltrating Type
Periductal-infiltrating cholangiocarcinoma grows along the bile ducts and
is therefore elongated, spiculated, or branchlike
(Fig. 5). Irregular narrowing
of the involved bile duct eventually results in obstruction. Most hilar
cholangiocarcinomas are of the periductalinfiltrating type, and it is
therefore difficult or impossible to depict the tumor mass on CT and
sonography [9,
26,
28].
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On imaging, the bile ducts proximal to the cholangiocarcinoma are dilated and the involved bile ducts are diffusely narrow or obliterated (Figs. 6A, and 6B). Nonunion of the right and left hepatic ducts with or without a visible thickened wall is a typical finding of infiltrating hilar cholangiocarcinoma [9, 27, 29]. On cholangiography, the lumen may be completely obstructed or markedly narrowed (Figs. 6A, and 6B). A stringlike, severely narrow bile duct may be visualized [28].
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Intraductal-Growing Type
Most intraductal-growing cholangiocarcinomas are papillary adenocarcinomas
[17-20],
comprising innumerable frondlike infoldings of proliferated columnar
epithelial cells and slender fibrovascular cores
[17]. The tumors are usually
small, sessile, or polypoid, often spreading superficially along the mucosal
surface and resulting in multiple tumors (papillomatosis) along various
segments of the bile ducts
[17-19].
Sometimes a large mass occludes the bile duct
[18,
20] (Figs.
7A, and
7B,
7C). Occasionally, the tumor
produces a profuse amount of mucus, resulting in partial biliary obstruction
[17,
18,
20].
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Papillary adenocarcinoma is a low-grade malignancy, often limited to the mucosa and invading the wall in the late phase [17]. Intraductal-growing cholangiocarcinoma is fairly common, accounting for 8-18% of reported cases [6-8]. In one series, it constituted 15% of all resected intrahepatic cholangiocarcinomas [18].
Bile ducts are dilated because of obstruction by a tumor, by sloughed tumor debris, or by an excessive amount of mucin [17]. The biliary tree is dilated diffusely, lobarly, or segmentally, somewhat reminiscent of bronchiectasis in the lung, or aneurysmally depending on the size of a tumor and the amount of mucin production [18, 20] (Figs. 7A, 7B, and 7C).
On sonography, CT, or MR cholangiography, the bile ducts of the involved hepatic segment or hepatic lobe are dilated. An intraductal mass can appear as an echogenic mass on sonography and as an enhancing soft-tissue mass on CT (Fig. 7A). The mass is confined within the bile ducts, and thus the wall of the bile duct remains intact. The outer margin of the thickened bile duct wall is smooth and clear. The tumor may not be depicted when it is small and isoattenuating to the adjacent hepatic parenchyma or when the complex orientation of the dilated bile ducts obscures the presence of the mass [7]. On endoscopic retrograde cholangiopancreatography or percutaneous transhepatic cholangiography, the involved biliary tree is dilated because of partial obstruction, and filling defects appear because of papillary tumors (Fig. 7B). There may be fine irregularities, a velvety or serrated contour along the bile ducts, representing the papillary surface of the tumor [17].
Intraductal Papillary Mucinous Tumor of the Bile Duct as a
Variant
Some papillary tumors of the bile ducts produce a large amount of mucin
[17,
18,
20] and may occasionally
impede the flow of bile juice, whereupon obstructive jaundice occurs.
Endoscopy may show mucin protruding from the patulous orifice of the duodenal
papilla. This tumor bears a striking similarity to intraductal papillary tumor
of the pancreas in terms of its histopathology, production of excessive mucin,
and pathophysiology. Sonography, CT, and MR cholangiopancreatography show
severe dilatation of the intraand extrahepatic ducts. Both proximal and distal
bile ducts to the tumor are dilated because mucin may obstruct the papilla of
Vater. On sonography and CT, the tumor may appear as a small mass.
Mucin is echo-free on sonography and water-attenuating on CT and therefore not visible. Endoscopic retrograde cholangiopancreatography or percutaneous transhepatic cholangiography can show large or small, elongated or amorphous filling defects caused by mucin in the dilated bile ducts [17] (Fig. 7B).
Some intrahepatic papillary mucinous tumors may produce aneurysmlike cystic dilatation of the bile ducts [17, 18, 20] that harbor multiple, fungating, intraductal papillary tumors (Fig. 7C). Some of the involved bile ducts dilate cystically, whereas others dilate diffusely and proportionally.
In short, mass-forming intrahepatic cholangiocarcinoma shows a large, well-defined, irregular mass with frequent satellite nodules, periductal-infiltrating cholangiocarcinoma results in obliteration of the bile ducts and proximal dilatation without an identifiable mass, and intraductal-growing cholangiocarcinoma presents with focal or segmental bile duct dilatation with or without visible intraductal papillary tumors.
Extrahepatic Cholangiocarcinoma
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TopIntroductionPathologic and Imaging FindingsIntrahepatic CholangiocarcinomaExtrahepatic CholangiocarcinomaMode of SpreadClinical SignificanceReferences |
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Mass-Forming Type
The tumor forms a nodule, which is usually 1-2 cm in diameter. The tumor
obstructs the bile duct lumen, penetrates the wall, and invades the periductal
tissue [6]. The luminal surface
is usually irregular [6].
On sonography, CT, MRI, MR cholangiography, or cholangiography, a mass-forming extrahepatic cholangiocarcinoma can be easily detected because the tumor occludes the bile duct and thus causes dilatation of the proximal bile ducts [27, 34] (Figs. 8A, 8B, and 8C). The bile ducts are usually completely obstructed at the time of diagnosis. Because the mass is generally small, images should be carefully scrutinized. On sonography, the mass may be masked by the surrounding soft-tissue structures or may be obscured by the adjacent bowel gas.
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Periductal-Infiltrating Type
The tumor appears as a diffuse, firm, gray-white, annular thickening of the
extrahepatic ducts with almost complete obstruction of the lumen
[6]. The thickness of the wall
increases up to 1 cm [6].
Concentric layering of cellular stroma around the neoplastic glands is the
most important identifying feature
[5]
(Fig. 9). The extent of the
tumor varies, ranging from 0.5 to 6 cm in length, sometimes involving all the
extrahepatic ducts and extending proximally as far as the intrahepatic ducts.
Associated tumor formation may occur outside the bile ducts in the
intrahepatic portion [33,
35,
36].
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On CT or MRI, the thickened bile ducts can be visualized as an enhancing ring or spot (Figs. 10A, 10B, and 10C). Sonography usually fails to depict the mass but shows focal or diffuse thickening of the bile duct [34]. The involved segment is variable, and the tumor border can be shown as an asymmetrically thickened bile duct wall at the transition zone [37] (Figs. 10A, 10B, and 10C). On cholangiography, the involved segment may not be opacified in cases of complete obstruction, or it may appear to be stringlike when the lumen is not completely obstructed (Figs. 10A, 10B, and 10C).
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Intraductal-Growing Type
In this type, the intraductal tumor may be polypoid, sessile, or
superficially spreading along the lumen
[17-20]
(Figs. 11A,
11B, and
11C). Discrete multiple tumors
(cholangiocarcinomatosis) may be present along the inner surface of the bile
ducts. Usually the tumor is limited to the mucosa and invades the wall and the
surrounding tissue in the very late phase
[17]. Intraductal papillary
cholangiocarcinoma is friable and sloughs easily when it is touched or rubbed
at the time of surgery. It can also slough spontaneously and, simulating bile
duct stones, occlude the bile ducts
[17].
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On imaging, the bile ducts proximal to the tumor are dilated, the degree of dilatation depending on the degree of obstruction. The intraductal tumor is depicted as a castlike or sessile mass on sonography, CT, or MR cholangiography [17]. Usually the tumor is small and flat, but occasionally it is large. The tumor tends to spread superficially along the lumen for a variable length and sometimes implants along the inner surface of the bile ducts, creating multiple discrete tumors [19] (Figs. 11A, 11B, and 11C). Cholangiography shows intraductal tumor or irregularity of the bile duct wall. Because the intraductal papillary tumor does not penetrate the bile duct wall, its outer margin is clear on sonography as well as on CT. Radiologic findings are basically the same as those for the intrahepatic intraductal form.
In short, mass-forming extrahepatic cholangiocarcinoma results in bile duct obstruction by a small mass; periductal-infiltrating cholangiocarcinoma produces segmental or diffuse, concentric thickening of the wall of the bile ducts without a focal mass; and intraductal-growing cholangiocarcinoma produces bile duct dilatation with single or multiple papillary intraductal masses.
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TopIntroductionPathologic and Imaging FindingsIntrahepatic CholangiocarcinomaExtrahepatic CholangiocarcinomaMode of SpreadClinical SignificanceReferences |
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Tumors arising from the mucosa of the extrahepatic duct grow intraluminally, invade the bile ductal wall, and eventually penetrate to the serosa [5, 6]. Because the intraluminal tumors easily occlude the lumen and cause obstructive jaundice at a relatively early stage, tumors of the extrahepatic ducts are small at the time of diagnosis, usually less than 2 cm.
Periductal-Infiltrating Cholangiocarcinoma
Cholangiocarcinoma arising from the mucosa of the intrahepatic bile ducts
invades the wall and penetrates to the serosa
[6]. In contrast to
mass-forming cholangiocarcinoma, periductal-infiltrating cholangiocarcinoma
tends to spread along the bile duct wall via the nerve and perineural tissue
of Glisson's capsule toward the porta hepatis
[1,
6]. Occasionally, a substantial
portion of the tumor tumor extends beneath the intact mucosal epithelium
[6]. Thus, the tumor grows
longitudinally and extends along the axis of the bile duct like a branch of a
tree [4]. Extrahepatic
periductal infiltrating tumor is characterized by concentric thickening of the
bile duct wall (the length of the thickening varies)
[5,
6]
(Fig. 9); it does not produce
a sizable mass.
Intraductal-Growing Cholangiocarcinoma
In intraductal-growing papillary cholangiocarcinomas, tumor cells are
confined within the mucosal layer and do not invade deep into the submucosal
layer; the tumor then spreads superficially along the mucosal layer. Because
the intraluminal papillary projections are slender and long, the tumor is
friable and may slough spontaneously
[17]. Sometimes, the detached
tumor implants at the lumen of the adjacent bile duct, resulting in multiple
tumors (papillomatosis) (Figs.
11A,
11B, and
11C).
It is postulated that when a tumor grows to a certain size, it sloughs spontaneously from the wall of the bile ducts. The sloughed and floating tumor debris may reside within the bile ducts, imbibing nutrients from the bile juice, and may grow substantially. These sizable tumors then float within the bile ducts and partially occlude the bile flow, or they may drain through the orifice of the papilla of Vater [17]. A similar phenomenon is also well known: hepatocellular carcinoma can be detached from the bile duct and grow within the bile ducts as an embolus [38, 39].
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TopIntroductionPathologic and Imaging FindingsIntrahepatic CholangiocarcinomaExtrahepatic CholangiocarcinomaMode of SpreadClinical SignificanceReferences |
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The surgical treatment should be tailored according to the gross morphology of the cholangiocarcinoma. To achieve a permanent cure, physicians should perform liver resection with a tumor-free margin in cases of the mass-forming type; but for cholangiocarcinomas of the periductal-infiltrating type, more aggressive surgery, including extensive liver resection, lymph node dissection, and adjuvant anticancer therapy, should be performed [12, 40]. For intraductal-growing cholangiocarcinomas, tumor resection with a tumor-free margin is sufficient, and long-term patient survival can be expected [17-19].
Acknowledgments
I thank Cheol Keun Park for his invaluable advice regarding the pathology
of cholangiocarcinoma and Bonnie Hami and Young Joo Moon for copyediting the
manuscript.
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TopIntroductionPathologic and Imaging FindingsIntrahepatic CholangiocarcinomaExtrahepatic CholangiocarcinomaMode of SpreadClinical SignificanceReferences |
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